Suzaku Spectral Observations of Magnetic Cataclysmic Variable (mCV) EX Hya

BY

E. Sudum and R.N.C. Eze

Introduction. 1. The Suzaku Telescope

2/2

8/2

01

4

Suza

ku s

pec

tral

Ob

serv

atio

n o

f M

agn

etic

Cat

acly

smic

Var

iab

le

(mC

V)

Ex H

ya. D

epar

tmen

t o

f P

hys

ics

and

Ast

ron

om

y U

NN

.

2

2. Intermediate Polars or DQ HER

2/2

8/2

01

4

Suza

ku s

pec

tral

Ob

serv

atio

n o

f M

agn

etic

Cat

acly

smic

Var

iab

le

(mC

V)

Ex H

ya. D

epar

tmen

t o

f P

hys

ics

and

Ast

ron

om

y U

NN

.

3

3. Polars or AM Her

2/2

8/2

01

4

Suza

ku s

pec

tral

Ob

serv

atio

n o

f M

agn

etic

Cat

acly

smic

Var

iab

le

(mC

V)

Ex H

ya. D

epar

tmen

t o

f P

hys

ics

and

Ast

ron

om

y U

NN

.

4

4. The iron Kα Line

5. Ex Hya

2/2

8/2

01

4

Suza

ku s

pec

tral

Ob

serv

atio

n o

f M

agn

etic

Cat

acly

smic

Var

iab

le

(mC

V)

Ex H

ya. D

epar

tmen

t o

f P

hys

ics

and

Ast

ron

om

y U

NN

.

5

For an electron to be excited from a state with energy E1 to a state with energy E2 it needs to absorb a photon of frequency

f = (E2 – E1)/h.

where h is the Planck's constant.

2/2

8/2

01

4

Suza

ku s

pec

tral

Ob

serv

atio

n o

f M

agn

etic

Cat

acly

smic

Var

iab

le

(mC

V)

Ex H

ya. D

epar

tmen

t o

f P

hys

ics

and

Ast

ron

om

y U

NN

.

6

2/2

8/2

01

4

Suza

ku s

pec

tral

Ob

serv

atio

n o

f M

agn

etic

Cat

acly

smic

Var

iab

le

(mC

V)

Ex H

ya. D

epar

tmen

t o

f P

hys

ics

and

Ast

ron

om

y U

NN

.

7

E1

Emission

2/2

8/2

01

4

Suza

ku s

pec

tral

Ob

serv

atio

n o

f M

agn

etic

Cat

acly

smic

Var

iab

le

(mC

V)

Ex H

ya. D

epar

tmen

t o

f P

hys

ics

and

Ast

ron

om

y U

NN

.

8

E2

E1

Absorption

2/2

8/2

01

4

Suza

ku s

pec

tral

Ob

serv

atio

n o

f M

agn

etic

Cat

acly

smic

Var

iab

le

(mC

V)

Ex H

ya. D

epar

tmen

t o

f P

hys

ics

and

Ast

ron

om

y U

NN

.

9

Hard X-rays

Bremsstrahlung/photoionization Fe

α li

ne

s/co

nti

nu

um

flu

x

Previous work • Kraft 1962, first discovered EX Hya and identified

it as an eclipsing system with an orbital period (Porb = 98 min).

• Watson et al. 1978, first discovered the X-ray emission in the quiescent state

• Beuermann & Osborne 1988, first reported a hard X-ray eclipse in EX hya

• Eisenbart et al. 2002, showed that the broad emission lines and the continuum flux in Ex hya are formed in an optically thick accretion curtain and from the innermost part of the accretion

curtain of the white dwarf itself.

2/2

8/2

01

4

Suza

ku s

pec

tral

Ob

serv

atio

n o

f M

agn

etic

Cat

acly

smic

Var

iab

le

(mC

V)

Ex H

ya. D

epar

tmen

t o

f P

hys

ics

and

Ast

ron

om

y U

NN

.

10

Previous work

• Scott et al. 2005, Reported that a strong Fe Kα line was detected in NGC 7469 with centroid energy of 6.39 ± 0.01 keV, and a line width 6310±1580 km s−1. No EW was given but the line flux was 3.9±0.7×10−5 photons cm−2 s−1.

• Evans et al. 2007, presented observations on NGC 2110. He measured the narrow Fe Kα line parameters E = 6.397±0.007 keV, and EW = 81+27

−30 eV. • Collinge et al. 2001, presented results from the Chandra HETGS

observation on NGC 4051 which showed that E = 6.41+0.01−0.01

keV, EW = 158+51−47 eV, and FWHM < 2800 km s−1 for the core of

the narrow Fe Kα line. • Eze, et al. 2013, reported that he hard X-ray from boundary

layers between the accretion and the compact objects irradiates the cold gas in the accretion disk leading to the emission of the Fe Kα fluorescence line.

2/2

8/2

01

4

Suza

ku s

pec

tral

Ob

serv

atio

n o

f M

agn

etic

Cat

acly

smic

Var

iab

le

(mC

V)

Ex H

ya. D

epar

tmen

t o

f P

hys

ics

and

Ast

ron

om

y U

NN

.

11

Source of data

Ex Hya was observed by Suzaku for 91 sec on July 18, 2007 (obsid 402001010). The data was processed using version 2.0 of the standard Suzaku pipeline software and the HEAsoft version 6.10. We downloaded Ex Hya data from suzaku achive.

2/2

8/2

01

4

Suza

ku s

pec

tral

Ob

serv

atio

n o

f M

agn

etic

Cat

acly

smic

Var

iab

le

(mC

V)

Ex H

ya. D

epar

tmen

t o

f P

hys

ics

and

Ast

ron

om

y U

NN

.

12

Data Analyses

• We used the XIS detectors to create source spectra. • We extracted the XIS background spectra. • We used xselect filter time file routine to extract the source and

background spectra for each observation. • We used xselect to extract Suzaku data into spectra, images, and

lightcurves.

The source and background integration regions of the Ex hya images taken with XIS1 at the XIS-default position (left) and the HXD-default position (right) on 2013 March 15. The background regions with a size of 126 by 1024 pixels each are taken at the left and right ends of the chip for the XIS-default position, and a source region with a size of 252 by 1024 pixels is taken at the side far from the Ex hya image for the HXD-default position. The remaining source-integration region has a size of 768 by 1024 pixels.

2/2

8/2

01

4

Suza

ku s

pec

tral

Ob

serv

atio

n o

f M

agn

etic

Cat

acly

smic

Var

iab

le

(mC

V)

Ex H

ya. D

epar

tmen

t o

f P

hys

ics

and

Ast

ron

om

y U

NN

.

13

Data Analyses contd.

• The HXD PIN detector analysis was done by first downloading non X-ray turned PIN background files and response matrices suitable for the observation to make the PIN NXB spectrum.

• We used the mgtime FTOOLs to merge the good time interval to get a common value for the PIN background and source event files.

• We used the hxddtcor in the suzaku FTOOLs to correct the dead time for the observed spectra.

• We used XSPEC version 12.7.0 for the spectral analysis of our data.

2/2

8/2

01

4

Suza

ku s

pec

tral

Ob

serv

atio

n o

f M

agn

etic

Cat

acly

smic

Var

iab

le

(mC

V)

Ex H

ya. D

epar

tmen

t o

f P

hys

ics

and

Ast

ron

om

y U

NN

.

14

Data Analyses contd.

• Errors in our work were obtained using the XSPEC error command.

• We modeled the spectrum using the absorbed bremsstrahlung model with three gaussian lines for the Fe Kα emission lines. Since we are primarily interested in the ion lines, our fitting covered 0 -10.0 KeV for the XIS BI, 3.0 -12.0 KeV for the XIS FI and 15.0 – 40.0 KeV for the HXD PIN.

• Energy below 3.0 KeV were ignored in the XIS FI and BI detector to avoid intrinsic absorption which is known to affect data at this energy range.

• energy above 10 KeV were also ignored for XIS BI due to high instrument background compared to the XIS FI detectors.

• We resolved the neutral or low-ionized (6.41 keV), He-like (6.70 keV), and H-like (7.00 keV) lines.

2/2

8/2

01

4

Suza

ku s

pec

tral

Ob

serv

atio

n o

f M

agn

etic

Cat

acly

smic

Var

iab

le

(mC

V)

Ex H

ya. D

epar

tmen

t o

f P

hys

ics

and

Ast

ron

om

y U

NN

.

15

Result and Discussion

Suzaku spectra of Ex Hya fitted with a simple absorber bremsstralung model (suited to highly ionized disks) showing a pointed X-ray spectral observations of Fe K due to irradiation of the accretion disk by the hard X-rays from the boundary layers, reprocessing in a dense absorber plus partial covering absorber of the system. The insert shows an expanded version of the resolved iron line complex

2/2

8/2

01

4

Suza

ku s

pec

tral

Ob

serv

atio

n o

f M

agn

etic

Cat

acly

smic

Var

iab

le

(mC

V)

Ex H

ya. D

epar

tmen

t o

f P

hys

ics

and

Ast

ron

om

y U

NN

.

16

Result and Discussion contd.

Light curve of Ex Hya showing no flare, signifying no intrinsic variation in the source during the observation.

2/2

8/2

01

4

Suza

ku s

pec

tral

Ob

serv

atio

n o

f M

agn

etic

Cat

acly

smic

Var

iab

le

(mC

V)

Ex H

ya. D

epar

tmen

t o

f P

hys

ics

and

Ast

ron

om

y U

NN

.

17

Result and Discussion contd. • A striking observation is the presence of strong H-

like and He-like emission lines detected at line centroid energy of 6.7 and 7.0 KeV,

• A detectable florescence of Fe XVIII-Fe XXIV lines producing Fe K lines.

• We assume that the observed continuum of Ex Hya is that which drives the line emission.

• Also, we assume that the observed reprocessed line emission created in the photo-ionized medium is completely unabsorbed but that of the bremsstrahlung is absorbed along our line of sight.

• With these assumptions, we deduced

2/2

8/2

01

4

Suza

ku s

pec

tral

Ob

serv

atio

n o

f M

agn

etic

Cat

acly

smic

Var

iab

le

(mC

V)

Ex H

ya. D

epar

tmen

t o

f P

hys

ics

and

Ast

ron

om

y U

NN

.

18

Result and Discussion contd. • A detection of strong iron lines and the bremsstrahlung continuum

with an average temperature of 10 KeV in the source support the thermal origin of the hard X-rays; hence these hard X-rays are most likely released during the accretion process within the boundary layer Eze, (2013).

• We however observed no absorption of the hard X-rays by full covering and partial covering in the source as shown in table 4.1.

• The light curve shows no intrinsic variations in the system during the observation.

• We find that a simple model of absorber bremsstrahlung spectra fits the data very well. The hard X-ray from boundary layers between the accretion and the compact objects irradiates the cold gas in the accretion disk leading to the emission of the Fe Kα fluorescence line (Eze, 2013 in press).

2/2

8/2

01

4

Suza

ku s

pec

tral

Ob

serv

atio

n o

f M

agn

etic

Cat

acly

smic

Var

iab

le

(mC

V)

Ex H

ya. D

epar

tmen

t o

f P

hys

ics

and

Ast

ron

om

y U

NN

.

19

Result and Discussion contd. Parameter Ex Hya (Value ± Error)

(KT) KeV 10.00 ± 1.00

photons s-1cm-2 (Fcounts) 20.80 ± 0.10

E6.4 (KeV) 6.41 ± 0.01

E6.7 (KeV) 6.66 ± 0.02

E7.0 (KeV) 6.95 ± 0.01

F6.4 in 10-5 photon s-1 cm-1 3.30 ± 0.20

F6.7 in 10-5 photon s-1 cm-1 2.90 ± 0.30

F7.0 in 10-5 photon s-1 cm-1 1.10 ± 0.30

EW6.4 in eV 28.00 ± 3.00

EW6.7 in eV 32.00 ± 1.00

EW7.0 in eV 109-4+5

2/2

8/2

01

4

Suza

ku s

pec

tral

Ob

serv

atio

n o

f M

agn

etic

Cat

acly

smic

Var

iab

le

(mC

V)

Ex H

ya. D

epar

tmen

t o

f P

hys

ics

and

Ast

ron

om

y U

NN

.

20

Origin Of Fe Kα Line In Ex Hya

1. the intense flux around the white dwarf due to collisional ionization because of the absence of absorption.

2. The detectable florescence of Fe XVIII-Fe XXIV lines and recombination to higher ionization state

3. In the hard X-rays from the boundary layers between the accretion disk and the white dwarf due to irradiation.

4. By the line energy range of 6.7-6.9KeV of H-like and He-like iron by bremsstrahlung cooling

5. Photoionization of the k-shell followed by florescence of atoms in ionized state

2/2

8/2

01

4

Suza

ku s

pec

tral

Ob

serv

atio

n o

f M

agn

etic

Cat

acly

smic

Var

iab

le

(mC

V)

Ex H

ya. D

epar

tmen

t o

f P

hys

ics

and

Ast

ron

om

y U

NN

.

21

Uses Of Fe Kα Lines in astrophysical sites

• They may serve as possible diagnostics of accretion flows and the structure of the source plasma in AGN

• Information from the iron line complexes are useful probe of the region very close to an accreting black hole

• Information from the iron line complexes can be used to probe and study black hole activities at the center of nearby galaxies

• Its width can as shown on the spectrum of an observed source can give kinematic information that can be used to estimate the size and location of the X-ray reprocessor

2/2

8/2

01

4

Suza

ku s

pec

tral

Ob

serv

atio

n o

f M

agn

etic

Cat

acly

smic

Var

iab

le

(mC

V)

Ex H

ya. D

epar

tmen

t o

f P

hys

ics

and

Ast

ron

om

y U

NN

.

22

Conclusion • We have shown that a bremsstrahlung model is capable of

reproducing the X-ray spectra revealing a pointed X-ray spectral signature of Fe K line of Ex Hya.

• The hard X-ray from boundary layers between the accretion and the compact objects irradiates the cold gas in the accretion disk leading to the emission of the Fe Kα fluorescence line in hard X-ray emitting symbiotic stars (Eze, et al. 2007).

• We resolved the neutral or low-ionized (6.41 keV), He-like (6.70 keV), and H-like (7.00 keV) Fe K line complex in the system.

• From our bremstrahlung model, the Fe K line complexes in Ex Hya at 6.41, 6.70 and 7.00 keV line originated by irradiation of the accretion disk by hard X-rays from the boundary layers between the accretion disk and the hot white dwarf, and by collisional ionization by intense X-ray flux round the white dwarf.

2/2

8/2

01

4

Suza

ku s

pec

tral

Ob

serv

atio

n o

f M

agn

etic

Cat

acly

smic

Var

iab

le

(mC

V)

Ex H

ya. D

epar

tmen

t o

f P

hys

ics

and

Ast

ron

om

y U

NN

.

23

Conclusion contd.

• The simplest physical interpretation of this model is that the bremsstrahlung represents the interstellar absorption component while the remaining two partial covering absorbers represent the phase dependent absorption caused by the accretion curtains.

• We however observed a high absorption of the hard X-rays by full covering and partial covering in all the sources as shown in table 4.1.

• The light curve shows no intrinsic variations in the system during the observation.

• We find that a simple model of absorber bremsstrahlung spectra fits the data very well.

• Hard X-rays are most likely released during the accretion process within the boundary layer of Ex Hya

2/2

8/2

01

4

Suza

ku s

pec

tral

Ob

serv

atio

n o

f M

agn

etic

Cat

acly

smic

Var

iab

le

(mC

V)

Ex H

ya. D

epar

tmen

t o

f P

hys

ics

and

Ast

ron

om

y U

NN

.

24

THANK YOU DAALU

NAAGODE ESHEI

2/2

8/2

01

4

Suza

ku s

pec

tral

Ob

serv

atio

n o

f M

agn

etic

Cat

acly

smic

Var

iab

le

(mC

V)

Ex H

ya. D

epar

tmen

t o

f P

hys

ics

and

Ast

ron

om

y U

NN

.

25